Caps lock abuse is just randomly typing in capital letters. This is no just using caps lock for important information, like:
WARNING: IF YOU CLICK THIS YOU WILL DIE.
That makes at least some sense. Caps lock abuse is more just rambeling nonsense that people use just to:
A. piss people off.
B. draw attention to themselves.
Sometimes, these people are just idiots that can't figure out how to get the caps lock thing off. Or maybe they just like typing in caps.

mrszjojonasz: HII MY NAME IISZ BAWB LOL UM I LIKE CHOCOLATE AND PONIIESZ AND THE JONAS BROTHERSZZZZ
theycallmeme: Get your hand off the caps lock button.
mrszjojonasz: WHAT ARE YOU TALKING ABOUT?
theycallmeme: You are an example of caps lock abuse. Goodbye.
-logs off-